Hey there Jenjenchik,
I apologize about the late response, thank you for being patient! I've talked to a higher tier of support about this in the past, and I was told that this is actually intended behavior. However, I know some people are not a fan of that, since sometimes the TV is set to a high volume as well. What I would recommend is that you submit feedback via the Google Home app to let Google know that you'd like that changed. While Google won't respond directly back to you, this is the best way to let Google know what changes you'd like to see.
I'm sorry I couldn't be more help, but if you have any other questions or concerns for me, please let me know.